Heat exchange system, cryogenic fluid vaporization

ABSTRACT

The invention provides a method and apparatus for heating and vaporizing a cryogenic fluid while controlling the heat flux of a plate fin and tube and finned tube exchanger by use of an intermediate fluid circuit.

TECHNICAL FIELD

This invention pertains to the field of heat exchange and specifically to utilizing a thermal fluid to control heat flux in the annular space of a double tube plate fin exchanger.

BACKGROUND OF THE INVENTION

Plate fin tube in tube heat exchangers or externally finned tube exchangers have long been employed to exchange heat, in varied applications. These exchangers are most often employed to heat or cool a low density gas stream located on the finned side against a denser fluid with higher heat transfer coefficient within the tubes. The extended surface on the finned exterior pass allows greater heat transfer surface than a bare tube and provides greater heat transfer at a low-pressure drop.

The art has not heretofore recognized the unexpected advantage that by controlling heat flux the use of cold or cryogenic fluids may be used on the internal tube and air or water containing fluids may be used on the exterior finned side reducing frosting or icing of the unit.

SUMMARY OF THE INVENTION

The invention may be employed to increase efficiency of any gas turbine by using cold or cryogenic fluids to cool inlet air. The invention can also be used to vaporize cryogenic fluids such as Liquefied Natural Gas (LNG) with ambient air with an intermediate fluid to control the heat transfer rate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sketch of a typical tube in tube coil with finned outer tubing.

DETAILED DESCRIPTION OF THE INVENTION

The invention may be described in several ways as alternate embodiments of the same novel discovery.

An energy exchange system that comprises:

-   -   a. Providing a first working fluid on the finned exterior side         of the heat transfer device,     -   b. Providing 2 or more working fluids flowing in separate         circuits within the internal circuits of the heat transfer         device,     -   c. feeding the first working fluid to the exterior finned side         of a heat transfer zone or zones to transfer heat from the first         working fluid thereby cooling the first working fluid to a lower         temperature,     -   d. feeding the second working fluid into passages or groups of         passages to be heated or cooled by the first working fluid,     -   e. feeding the third working fluid(s) into a separate passage or         group of passages to be heated by the second working fluid,     -   f. feeding the second fluid into a passage or group of passage         space(s) between the first working fluid exterior finned side         and the third working fluid passage or group of passages to         control heat flux to minimize freezing of the first working         fluid on the exterior finned side.         In a preferred embodiment the invention provides:     -   g. in a heat exchange device having one or more finned exterior         side working fluid streams against one or multiple inner passage         circuits,         In a more preferred embodiment the invention further provides         the steps of:     -   h. A method of circuitry of a plate fin and tube or finned tube         exchanger that allows for more effective heat transfer by         controlling the heat flux,         In a more preferred embodiment the invention provides:     -   i. Causing ambient air to be passed across the exterior finned         side of a finned tube exchanger which contains a cryogenic fluid         being heated and vaporized in an inner tube or group of tubes,         and which utilizes an intermediate fluid in the space between         the inner tube and the outer tube of each circuit to control         heat transfer rate thereby reducing frosting or icing of the         ambient air.

In a more preferred embodiment of the invention i. above, the intermediate fluid in the space between the inner and outer tube or group of tubes is caused to flow by pumping or other means thereby allowing improved heat transfer while reducing frosting or icing of the outer finned surface.

In summary, the invention provides a system for controlled heat transfer in a plate fin and tube or finned tube exchanger by using an intermediate fluid.

The invention is defined and limited by the claims set out below. 

1. A method of recovering energy that comprises: a) Providing a first working fluid on the finned exterior side of the heat transfer device, b) Providing 2 or more working fluids flowing in separate circuits within the internal circuits of the heat transfer device, c) feeding the first working fluid to the exterior finned side of a heat transfer zone or zones to transfer heat from the first working fluid thereby cooling the first working fluid to a lower temperature, d) feeding the second working fluid into passages or groups of passages to be heated or cooled by the first working fluid, e) feeding the third working fluid(s) into a separate passage or group of passages to be heated by the second working fluid, f) feeding the second fluid into a passage or group of passage space(s) between the first working fluid exterior finned side and the third working fluid passage or group of passages to control heat flux to minimize freezing of the first working fluid on the exterior finned side.
 2. The method of claim 1 further comprising: a. A method of circuitry of a plate fin and tubes or finned tube exchanger that allows more effective control of heat flux by use of an intermediate fluid.
 3. An apparatus for employing the method of claim 1 comprising: a. Causing ambient air to be passed across the exterior finned side of a finned tube exchanger which contains a cryogenic fluid in an inner tube or group of tubes which is heated or vaporized, and which utilizes an intermediate fluid in the space between the inner tube and the outer tube of each circuit to control heat transfer rate, thereby reducing frosting or icing of the ambient air.
 4. In a more preferred embodiment of claim 3 above, the apparatus contains an intermediate fluid in the space between the inner and outer tube or group of tubes which is caused to flow by pumping or other means, thereby allowing improved heat transfer which reduces frosting or icing of the outer finned surface.
 5. The method of claim 1 wherein the first working fluid and the second working fluid have the same composition.
 6. A heat transfer apparatus of claim 3 which cools inlet air to a gas turbine or combustion source while heating or vaporizing Liquefied Natural Gas (LNG) or Liquefied Petroleum Gas (LPG).
 7. A method for designing an energy recovery system or inlet cooling for increasing the efficiency or power output of a gas turbine by providing an intermediate fluid controlled tube side heat flux while heating or vaporizing a cryogenic fluid(s) used to cool turbine inlet air.
 8. The apparatus of claim 3 that will control heat flux and provide secondary containment of the cryogenic fluid and will allow leak detection of the cryogenic fluid in the intermediate fluid circuit.
 9. A device for heating and vaporizing LNG by using ambient air as the heat source. The cryogenic vaporizer comprising a finned tube surface or plate fin and tube air side flow path with an intermediate fluid in a separate flow circuit to control the heat transfer rate between the LNG and air.
 10. An apparatus as described in claim 3 above which uses an intermediate fluid possessing the characteristics of a freeze point between −325 deg F. and 35 deg F., and which has a density greater than 1 pound/ft3.
 11. A device as described in claim 3 above utilizing an intermediate fluid composed at least 5% by weight of a glycol, a hydrocarbon, refrigerants listed by ASHRAE, an alcohol, a formate, ammonia, salt brines, or aquaus solutions.
 12. A method as described in claim 1 above which uses an intermediate fluid possessing the characteristics of a freeze point between −325 deg F. and 35 deg F., and which has a density greater than 1 pound/ft3.
 13. A method as described in claim 1 above utilizing an intermediate fluid composed at least 5% by weight of a glycol, a hydrocarbon, refrigerants listed by ASHRAE, an alcohol, a formate, ammonia, salt brines, or aquaus solutions.
 14. A method as described in claim 1 above utilizing an intermediate fluid where the intermediate fluid is heated in a separate external heater under conditions when the temperature of ambient air is such that cooling the air will cause frosting or freezing of water from the air on the external finned surface.
 15. A device as described in claim 3 above utilizing an intermediate fluid where the intermediate fluid is heated in a separate external heater under conditions when the temperature of ambient air is such that cooling the air will cause frosting or freezing of water from the air on the external finned surface. 